6) Ocular Blood Supply

Internal carotid artery

supplies the anterior brain.

branches from the Common carotid artery.

enters the cranium through the Carotid canal, passes through the Cavernous sinus, and divides into the:

1. Ophthalmic artery

2. Posterior communicating artery

3. Anterior choroidal artery

4. Anterior cerebral artery

5. Middle cerebral artery

OPAAM

Vertebral artery

supplies the posterior brain.

branches from the Subclavian artery.

enters the cranium through the Foramen magnum.

Basilar artery

Vertebral arteries fuse to form the Basilar artery

Cerebral arterial circle (Circle of Willis)

complex of anastomosing arteries that includes:

1. Internal carotid arteries

2. Anterior cerebral arteries, linked by

3. Anterior communicating artery

4. Posterior cerebral arteries, linked to Internal carotids by

5. Posterior communicating arteries

IPAPA

terminal branches of Internal carotid artery

-Anterior cerebral arteries.
-Middle cerebral arteries

Anterior cerebral artery: where does it supply blood to?

anteriomedial portion of the cerebrum (in yellow)

Middle cerebral artery: where does it supply blood to?

the majority of the lateral brain (in red)

Posterior cerebral artery: where does it supply blood to?

medial & lateral parts of the posterior cerebrum (in blue)

***problems with the Posterior cerebral artery can affect vision/visual cortex!

which artery/arteries supply the Optic chiasm?

Anterior cerebral artery

which artery/arteries supply the Optic tract?

Anterior choroidal artery

which artery/arteries supply the Lateral Geniculate Nucleus (LGN)?

-Anterior choroidal artery
-Posterior cerebral artery

which artery/arteries supply the 1st Visual Cortex?

-Middle cerebral artery

-Posterior cerebral artery (!!!)

Cavernous sinus

Internal carotid artery enters the skull via Carotid canal, then enters the Cavernous sinus.

contains oculomotor, trochlear, abducens, ophthalmic, and maxillary nerves (3, 4, 6, V1, V2).

the Ophthalmic artery is the first branch of ICA as it leaves the Cavernous sinus.

Ophthalmic artery

the main blood supply to the globe and ocular adnexa.

enters the orbit through the Optic foramen.

branches:

1. Central Retinal

2. Lacrimal

3. Lateral & Medial Posterior Ciliary (→Long & Short PCAs)

4. Ethmoidal

5. Supraorbital

6. Muscular (Lateral & Medial)

7. Medial Palpebral (Superior & Inferior)

8. Supratrochlear

9. Dorsonasal

Branches of the Ophthalmic artery: Orbital group

distributed to the orbit and surrounding parts.

includes:

-Lacrimal

-Supraorbital

-Ethmoidal (Anterior & Posterior)

-Medial Palpebral

-Supratrochlear

-Dorsonasal

Lacrimal artery

runs along upper border of LR.

supplies the lacrimal gland.

terminates at lateral palpebral arteries.

Supraorbital artery

supplies SR, SO and levator.

supplies skin & muscles of the scalp.

Ethmoidal (Anterior & Posterior) arteries

supplies ethmoid, frontal, and sphenoid sinuses.

supplies the nasal cavity & skin of the nose.

Medial Palpebral artery

branches into palpebral arcades.

supplies superior & inferior eyelids.

Supratrochlear artery

supplies the forehead.

Dorsonasal artery

supplies the lacrimal sac.

supplies the outer nose.

Branches of the Ophthalmic artery: Ocular Group

distributed to the muscles and bulb of the eye.

includes:

-Central Retinal

-Muscular

-Anterior Ciliary

-Long & Short PCAs

Central Retinal artery

pierces sheath and enters the optic disc on the nasal side.

branches into superior, inferior, nasal, & temporal.

gives off meningeal branches to supply the pia mater of the optic nerve.

Medial and Lateral PCAs (MPCAs & LPCAs)

the major blood supply to the globe.

branches into Long & Short PCAs

→ can have variable branching

Long PCAs

paired (2) arteries that pierce the sclera and travel within the suprachoroidal space to the ciliary body.

supplies the choroid anterior to the equator.

combine with ACAs to form MACI

Short PCAs (SPCAs)

10-20 branches pierce the sclera around the optic nerve.

→ forms the circle of Zinn

supplies the optic nerve head

supplies the choroid posterior to the equator.

Cilioretinal artery

comes out of the temporal aspect of the optic nerve head and supplies the macula.

branches from short PCAs (not from CRA)

advantageous in cases of CRA occlusion

→ if there is CRAO, some blood flow to the macula is preserved via cilioretinal arteries.

Anterior ciliary artery (ACA)

from the EOMs.

two ACAs for each rectus muscle

→ except LR muscle only has 1!

→ 7 ACAs total per eye

supplies the sclera, conjunctiva, and iris.

Nerve Loop of Axenfeld

a branch of the Long ciliary nerves reaches the surface of the sclera, forming a visible nodule.

the Anterior ciliary artery can be seen near the nerve loop.

Muscular artery (Lateral)

superior artery.

supplies LR, SR, SO, and Levator muscles.

Muscular artery (Medial)

inferior artery.

supplies MR, IR, and IO muscles.

which EOM is the only one to receive blood supply ONLY from the Muscular artery?

Medial rectus

Medial rectus blood supply

Medial muscular artery ONLY

2 ACAs

Lateral rectus blood supply

Lateral muscular artery
Lacrimal artery

1 ACA

Inferior rectus blood supply

Medial muscular artery
Infraorbital artery

2 ACAs

Superior rectus blood supply

Lateral muscular artery
Supraorbital artery

2 ACAs

Inferior oblique blood supply

Medial muscular artery
Infraorbital artery

Superior oblique blood supply

Lateral muscular artery
Supraorbital artery
Supratrochlear artery

External carotid artery

supplies the ocular adnexa.

branches from the Common carotid artery.

branches into:

-Facial artery

-Superficial Temporal

-Maxillary artery

Facial artery

branches into Angular artery.

supplies the nose.

Superficial Temporal artery

branches into Anterior Temporal anastomoses.

→ contains Supraorbital & Supratrochlear arteries

branches into Zygomatic & Transverse Facial arteries

→ supplies orbicularis.

Maxillary artery

branches into Infraorbital artery.

→ Infraorbital groove → Infraorbital foramen → supplies IR, IO, and lacrimal sac

veins have the same name as their paired arteries, except for...?

External Carotid artery & Internal Jugular vein

how does venous blood leave the eye?

via four pathways:

-Central Retinal Vein

-Vortex veins

-Anterior Ciliary veins

-Episcleral veins

what does the Central Retinal vein drain?

inner retina

what do the Vortex veins drain?

choroid

what do Anterior Ciliary veins drain?

ciliary body

return via Muscular veins

where do these veins drain to?

Superior & Inferior Ophthalmic veins, which combine behind the orbit and drain to the Cavernous sinus.

Superior Ophthalmic vein

drains superior orbit

exits the orbit through the Superior orbital fissure

Inferior Ophthalmic vein

drains LR, conjunctiva, lacrimal sac, lower vortex veins.

exits the orbit through the Inferior orbital fissure

Central Retinal vein

either joins with Superior Ophthalmic vein, or drains directly to Cavernous Sinus.

where does Cavernous sinus drain to?

Cavernous sinus (and other brain veins) all drain to the Internal Jugular vein

what do Infraorbital veins drain?

the face

Lymphatic drainage system

immune function - activated when there is an infection.

Retroauricular nodes: behind the ear

Preauricular nodes: in front of the ear

Submandibular nodes: below the mandible

Spontaneous Venous Pulsation (SVP)

normal subtle pulsations of the retinal vein(s) as they cross the optic disc.

caused by variation in the pressure gradient between retinal veins and CRV.

IOP > CSF (intracranial) pressure

once CSF pressure increases, SVP will stop.

Papilledema

CSF (intracranial) pressure > IOP

increased intracranial pressure can compress CRV, causing a blockage, causing edema of the optic disc.

evident as blurred disc margins, sometimes with hemorrhages.

no venous pulsations

Giant cell arteritis (GCA)

aka Temporal arteritis.

most common form of systemic inflammatory vasculitis in adults/elderly.

inflammation of medium and large sized blood vessels

Prodrome Sx: HA, fatigue, fever, sudden blurry vision

Carotid-Cavernous Sinus Fistula (CCF)

abnormal communication between the ICA and Cavernous Sinus.

caused by a tear in the artery wall.

veins may become pulsatile.

can increase aqueous outflow resistance, leading to high IOP.

Fluorescein Angiography (IVFA)

fluorescein dye can be injected to examine choroidal and retinal circulation.

within 10 seconds, choroidal flush

→ dye leaks out of fenestrated choriocapillaris

→ dye should NOT leak into the retina because RPE is not fenestrated

within 12 seconds, retinal arteries fill, then retinal veins.

defects in the RPE can be seen if the dye leaks into the retina BEFORE the retinal vessels fill (during choroidal flush)

Branch Retinal Venous Occlusion (BRVO)

occurs when thickened or hardened retinal arteries cross over a retinal vein and block it.

when the vein is blocked, nerve cells within the eye may die.

Anterior Ischemic Optic Neuropathy (AION)

results from nonperfusion/hypoperfusion of the ciliary blood supply to the optic nerve head.

nonatheritic AION can cause altitudinal vision field loss.